I presume your referring to the Rolls Royce Phantom and Drophead?
If so, it would depend entirely on your age / situation, whether you want a driver or want to drive yourself etc. If I was getting one at the age of 19 I would go for the Drophead. Interior-wise both are pretty much the same. My uncle has a Phantom and I've had a good look at the Drophead and apart from the awesome wooden, decking type thing the convertible has the interior is very similar. The Drophead also has more up-to-date styling and will age better. The headlights on the Phantom seem to be showing age already.